Shiranui Mandarin

Shiranui (不知火) is a Japanese citrus cultivar from a 1972 Kiyomi × Nakano No. 3 Ponkan cross at Kuchinotsu. UCR describes large fruit with a prominent stem-end knob; the neck can vary from pronounced to nearly absent, and the rind can be rough or coarse while remaining easy to peel.^{⁠[24]⁠[25]⁠[1]⁠[3]⁠[12]}

Seed set varies between accessions and growing situations. UCR reports many seeds in public accession CRC 4249 / VI 860, while also noting seedless fruit from isolated trees and identifying nearby pollen as a likely influence. IDtools’ seedless description applies specifically to clone DPI-132; Greg Alder likewise reports seedless fruit from his own tree. None of these observations guarantees seedlessness in every planting.^{⁠[1]⁠[7]⁠[12]}

Names used for Shiranui vary by market. UCR describes Dekopon for fruit marketed from Kumamoto, Kiyopon in Hiroshima, and Hallabong in Korea; Sumo Citrus is a commercial brand whose own history says its U.S. seedlings arrived in 1998 and the brand debuted publicly in 2011.^{⁠[1]⁠[11]}

Harvest timing depends on location. UCR lists December–February for CRC 4249 / VI 860 at Riverside, while Greg Alder says he generally starts picking his own tree in February. A Lower Mainland container grower reports one May 30 harvest and a 221 g fruit, with rainy weather raising concern about mold and premature picking; this is a single grower observation, not a regional harvest window.^{⁠[1]⁠[12]⁠[17]}

Shiranui is valued for rich, sweet mandarin flavor, although ripeness and handling affect the balance of sweetness, acidity and juiciness. The Mulberries store-fruit tasting reported 18 °Bx and pH 4.3. Separate home-grown and store-fruit comparisons reported readings from about 17 to 21 °Bx, with the highest readings taken twice from one follow-up fruit. These are individual samples rather than a cultivar-wide range.^{⁠[12]⁠[5]⁠[14]⁠[22]}